1. Field of the Invention
The present invention relates to a GaN substrate having high light transmittance in a red light region or in a visible light region from blue to red and having high conductivity as well as a light-emitting device including such a GaN substrate.
2. Description of the Background Art
A substrate having high light transmittance and high conductivity is demanded as a substrate for use in a light-emitting device. For example, Japanese Patent Laying-Open No. 2005-213075 (Patent Document 1) discloses a GaN substrate having an absorption coefficient from 7 cm−1 to 68 nm−1 for light having a wavelength from 375 nm to 500 nm. In addition, Japanese Patent Laying-Open No. 2007-126320 (Patent Document 2) discloses obtaining a GaN substrate of which absorption coefficient for light having a wavelength not shorter than 380 nm is lower than 7 cm−1, with a method of forming a TiN thin film having a large number of small holes on the substrate and growing a GaN crystal on the TiN thin film while suppressing introduction of an impurity other than Si (this method being referred to as a VAS (Void-Assisted Separation) method)).